WASHINGTON — The partial government shutdown and steep federal spending cuts helped lower the U.S. federal deficit last month, signaling more improvement in the government’s finances. The Treasury Department says the government ran a deficit of $91.6 billion in October, down 24 percent from the same month a year ago. The decline comes after the government ran an annual deficit of $680 billion for the 2013 budget year that ended on Sept. 30, the lowest in five years. Spending fell 5 percent in October to $290.5 billion, partly because of the shutdown and because of across-the-board spending cuts put in place earlier this year. Tax revenue rose 8 percent in October compared with a year earlier to $199 billion. Higher taxes and modest economic growth have helped boost revenue this year.